1. Field of the Invention
The present invention relates to an image forming apparatus and method. More specifically, the present invention relates to an image forming apparatus and method in which a controller controls a charger such that a current supplied from the charger to a battery changes based on a detected current supplied to the image forming apparatus.
2. Description of the Related Art
A background image forming apparatus such as a copier, a facsimile, or a printer fixes a toner image onto a record medium with heat to make a copied or a recorded medium. The toner image is fixed via a fixing device onto the record medium, because the toner image melts, softens and permeates into the record medium. The record medium is also conveyed while being nipped in the fixing device.
Japanese Published Unexamined Patent Application No. 2002-184554 shows an image forming apparatus including a heater and a battery. In this application, the temperature of the heater can be rapidly increased because the battery supplies power to the heater.
Further, Japanese Published Unexamined Patent Application No. Hei 10-282821 shows an image forming apparatus including a heater, a main power source and a battery. In this application, the battery is charged by the main power source during a standby time, and the battery discharges energy to the heater during a ramp-up period.
Turning now to FIG. 3, which illustrates a portion of a background image forming apparatus. As shown, the portion 20 of the image forming apparatus includes a controller 3 with a driver (not shown), a fixing device 4, a heating switch 7, a charger 8, a switching member 9, a battery 10, a voltage detector 11 for detecting a voltage of the battery 10, and a power source 21. The power source 21 is supplied with power from an external power source 2 and supplies power for driving, e.g. 24V, and for controlling (e.g. 5V) to the controller 3. The fixing device 4 includes a fixing member and a member opposite to the fixing member (not shown), a temperature sensor 22 for detecting a temperature of the fixing member, a first heater 5 and a second heater 6 both configured to heat the fixing member. The fixing member and the member opposite to the fixing member form a nip in which a record medium is passed between. Further, the switching member 9 includes a charging switch for connecting or disconnecting the charger 8 to the battery 10 and a discharging switch for connecting or disconnecting the battery 10 to the second heater 6.
According to the structure described above, the charger 8 charges the battery 10 via the outside power source 2 when the switching member 9 connects the charger 8 to the battery 10. In addition, the battery 10 supplies power to the second heater 6 when the switching member 9 connects the battery 10 to the second heater 6, and meanwhile the outside power source 2 supplies power to the first heater 5 independently of the battery 10. Further, the controller 3 is supplied with power from the power source 21, and receives a temperature detecting signal A from the temperature sensor 22 and a voltage detecting signal B from the voltage detector 11. Based on the signal A and B, the controller 3 outputs a control signal C to switch on-off the heating switch 7 and a control signal D to switch the switching member 9.
Thus, the first heater 5 and the second heater 6 heat the fixing member, and thereby a toner image is heated by the fixing member and fixed onto the record medium while passing through the nip.
Next, FIG. 4A illustrates a timing diagram showing power supplied from the outside power source 2 to the background image forming apparatus without the second heater 6 as a comparative example, and FIG. 4B is a timing diagram showing power supplied from the outside power source 2 to the background image forming apparatus with the second heater 6.
In the background image forming apparatus in FIGS. 3 and 4B, the controller 3 controls the switching member 9 such that the battery 10 connects to the heater 6 during a ramp-up period. Thereby, it is possible to rapidly raise the temperature of the fixing member and thus shorten the ramp-up period. Meanwhile, the controller 3 controls the switching member 9 such that the charger 8 is connected to the battery 10 during a standby time. Therefore, the battery 10 is charged until a necessary voltage is achieved to supply power to the heater 6 at the next ramp-up period.
However, the present inventor determined that the background image forming apparatus does not efficiently charge the battery 10 as described below. In more detail, FIG. 5 is a table showing the relation between a copying speed and a standard of energy consuming rate for a copier using an A3 size record medium. The table is based on a target standard in 2006 in the Japanese Rationalization in Energy Use Law. The following expression is a calculated result of the energy consuming rate in FIG. 4A when the copying speed is more than 40 and not more than 50. The electric energy is 800 W*3 min during a ramp-up period, 1100 W*2 min during copying, 180 W*15 min during a standby time, and 80 W*40 min during a low-power mode. That is, (800*3)+(1000*2)+(180*15)+(80*40)/60=171.6<176 Wh/h so the target standard is satisfied.
Further, the following expression is a calculated result of the energy consuming rate in FIG. 4B, when the charging energy is 150 W*15 min during copying, the ramp-up period is 1 min, and thereby the low-power mode is 42 min in addition to the above condition. That is, (800*1)+(1000*2)+(330*15)+(80*40)/60=185.2>176 Wh/h and the target standard is not satisfied.